This invention is directed to a system for disinfecting water generally for use for individual buildings or transient public water systems, such as at a store or other commercial establishment, or other public space, such as an airport. It has become extremely important today, in most sections of the world, to clean household water before use, including the killing of microbial parasites that cause illness and even death in humans. Such systems are referred to as “point of use (“POU”)” water disinfecting systems, where a single structure receives water, for example, from a well or stream of somewhat unclean provenance.
Water can be rendered microbe-free and parasite-free by the use of filtration systems which tend to be costly, except for individual use, or for entire homes, require expert care. Water can also be disinfected by exposure to ultra-violet radiation or to high temperatures, where the water is boiled for several minutes. This is generally not effective or practical for a building system, although it may be useful, for example, when camping out. Chemical disinfection is generally considered the most reliable and practical way to proceed, with the most common chemical used being a chlorinating material. Such chlorinating materials, such as hypochlorites, are especially useful for disinfecting water, as it is relatively simple to provide a concentration of chlorine in the water sufficient to kill any parasites living in the water, including bacteria, viruses and cysts or other creatures that may invade the human system, but below the concentration that will cause harm to the health of an individual person. Other materials which have been used include iodination systems and oxidizing systems based upon the addition of ozone or a peroxide or permanganate chemical. Such materials are effective but it has been found that because there is no residual effect, they are not sufficient to maintain a pure system where water is stored before use. In addition to removing harmful parasitic agents, including microbes, chlorination is also useful to oxidize inorganic materials which cause odor or turbidity in the water, such as iron, manganese and sulfur compounds, such as the oxides or hydrogen sulfide.
It has been found that in order to properly and safely use chlorinating compounds, it is necessary to ensure that the compounds are uniformly mixed throughout the water system and that there be sufficient resident time to ensure that the chlorine compounds have time to act to reduce the pH of the water and to kill any parasitic agents living in the water. Useful such chlorinating agents include, for example, sodium hypochlorite or calcium hypochlorite. Although chlorine gas can be used, it is generally not considered practical for use for individual households. The hypochlorite can be added as a divided solid or as a liquid solution in water.
In the United States, at least, the basic concept for a suitable chlorination disinfecting system is determined by calculating a value referred to as “CT”, where C represents a concentration of free chlorine residual in mg/l and T is contact time in minutes; the contact time is determined based upon the flow rate of the system and the size of the holding tank.
It has also been recognized that baffling of the flow through the tank is important in order to ensure uniform mixing of the disinfecting compound in the water. Examples of such prior baffling are shown for example in an article entitled “Disinfection”.